Printed circuit boards including strip-line circuitry and methods of manufacturing same

ABSTRACT

A printed circuit board includes a first layer stack and a second layer stack coupled to the first layer stack. The first layer stack includes a first electrically-insulating layer, a first electrically-conductive layer, and a cut-out area defining a void that extends therethrough. The first electrically-insulating layer includes a first surface and an opposite second surface. The first electrically-conductive layer is disposed on the first surface of the first electrically-insulating layer. The second layer stack includes a second electrically-insulating layer. The second electrically-insulating layer includes a first surface and an opposite second surface. One or more electrically-conductive traces are disposed on the first surface of the second electrically-insulating layer. The printed circuit board further includes a device at least partially disposed within the cut-out area. The device is electrically-coupled to one or more of the one or more electrically-conductive traces disposed on the first surface of the second electrically-insulating layer.

BACKGROUND

1. Technical Field

The present disclosure relates to strip-line circuitry. Moreparticularly, the present disclosure relates to printed circuit boardsincluding strip-line circuitry and methods of manufacturing the same.

2. Discussion of Related Art

Commonly used techniques for circuit and/or system interconnect includemicrostrip and strip-line transmission lines. In a simplerepresentation, as shown in FIG. 1, a microstrip transmission lineconsists of a conductive trace 13 of controlled width W_(C) disposed ona low-loss dielectric 11 which is, in turn, disposed on a ground-planelayer 12. In microstrip there is one ground plane, while in strip-line,there are two.

Microstrip and strip-line transmission lines can be fabricated usingprinted circuit board technology. Printed circuit boards (PCBs),sometimes referred to as printed wiring boards (PWBs) or etched wiringboards, are widely used in the assembly of discrete electricalcomponents into operating circuits. PCBs generally provide a reliableand economical means of interconnecting electrical signals betweensystem components. PCBs are available in a variety of different typesand may be classified in a variety of ways.

PCBs are generally used to mechanically support and electrically connectelectronic components using electrically-conductive pathways or signaltraces that conduct signals on the PCB. A typical PCB includes one ormore layers of insulating material upon which patterns of electricalconductors are formed. In addition to a pattern of conductive traces onthe PCB, a patterned array of metal-filled through-holes, or vias, maybe formed to allow for layer-to-layer interconnections between variousconductive features.

PCBs may be classified as single-sided PCBs, double-sided PCBs, andmulti-layer PCBs, according to the number of circuit pattern surfaces.Microstrip transmission lines, for example, are commonly fabricated ondouble-sided PCBs. PCBs may include circuits that perform a singlefunction or multiple functions.

A typical PCB may include a variety of electronic components. Electroniccomponents form parts of electronic circuitry and may be classified in avariety of ways. An electronic component may be classified as active orpassive. In general, an active component is any type of circuitcomponent with the ability to electrically control the flow of electronsor other electrically-charged particles. Some examples of activecomponents are transistors, integrated circuits (ICs),silicon-controlled rectifiers (SCRs), and triodes for alternatingcurrent (TRIACs). Components incapable of controlling current by meansof another electrical signal are generally classified as passivecomponents. Examples of passive components include capacitors,resistors, inductors, transformers, and diodes. A PCB on whichelectronic components are mounted is sometimes referred to as a printedcircuit assembly (PCA) or a printed circuit board assembly (PCBA).

In some circuits, such as high-frequency circuits, e.g., microwavecircuits, maintaining controlled impedance across the PCB may berequired in order to achieve consistent electrical performance, e.g., interms of amplitude and phase response. A variety of PCB trace geometriesare possible with controlled impedance designs. A two-sided PCB designwherein a planar conductor line is spaced above a ground plane, as shownin the cross-sectional view of FIG. 1, can be designed for controlledcharacteristic impedance. This geometry is known as a surfacemicrostrip, or simply microstrip. In microstrip the planar conductorlines are usually formed by chemically etching away unwanted areas ofmaterial, e.g., metal, from a conductor layer, such as copper.

The impedance of a planar conductor in a microstrip transmission lineformat is determined by factors such as the dielectric characteristicsof the surrounding materials, the width of the conductor line and itsspacing from the ground-plane layer, among other things. In the surfacemicrostrip configuration the signal conductor is exposed to air, so theeffective dielectric constant impacting the impedance of the conductoris a combination of the relative dielectric constant, ∈_(r), of the PCBdielectric substrate as well as that of the air above the circuit.Typically, the effective dielectric constant will be somewhere between 1(∈_(r) of air) and about 4 (∈_(r) of FR-4 substrate).

An approximate expression of the characteristic impedance Z₀ of amicrostrip transmission line, as shown in FIG. 1, is given by Equation 1(below) and is expressed in Ohms (Ω). In Equation 1, the measurementunit is mils, i.e., 1 mil=0.001 inches.

FIG. 1 shows a microstrip transmission line 10 that includes a signaltrace 13 on the top side of a PCB dielectric substrate 11 and a ground(or power) plane 12 on the bottom side of the substrate 11. UsingEquation 1, for the signal trace 13 of width W_(C) and thickness T_(C),separated by distance T_(D) from the ground plane 12 by the PCBdielectric substrate 11, the characteristic impedance Z₀ of themicrostrip line 10 may be expressed as

$\begin{matrix}{{{Z_{0}(\Omega)} \approx {\frac{87}{\sqrt{ɛ_{r} + 1.41}}\mspace{14mu}{\ln\left\lbrack \frac{5.98T_{D}}{\left( {{0.8W_{C}} + T_{C}} \right)} \right\rbrack}}},} & \left( {{Equation}\mspace{14mu} 1} \right)\end{matrix}$where ∈_(r) is the dielectric constant of the PCB substrate 11. Equation1 is generally valid when 0.1<W_(C)/T_(D)<2.0 and 1<∈_(r)<15.

Microstrip transmission line operation may be impaired by strayelectromagnetic coupling between the line conductor and nearby objects.In microstrip, the line conductor is coupled to the ground plane below,which reduces EMI (electromagnetic interference) by absorbing some ofthe electromagnetic field lines. Fringing of the electromagnetic fieldsthat extend above the line conductor to foreign objects may introduceirregularities into the impedance and velocity factor of the line, witha resultant negative effect on circuit performance. To mitigate theeffects of electrical field fringing, additional constraints may beimposed, e.g., requiring the width of the ground plane be such that itextends past each edge of the signal trace by at least the width of thesignal trace.

Strip-line transmission line construction, as shown in thecross-sectional view of FIG. 2, is generally characterized by a planarconductive trace 23 sandwiched by dielectric material 21 and disposedbetween two ground or power planes (commonly referred to as referenceplanes). An electric field 46 is generated between the conductor line 23and the upper and lower ground layers 24 and 22, and a magnetic field 58is generated around the conductor line 23. In strip-line routing, thesecond ground (or power) plane, which is omitted in microstripconstruction, shields the conductor from the effects of nearby objectsand serves to confine the electromagnetic fields to the region betweenthe two reference planes.

In strip-line routing, all of the electromagnetic field lines arecoupled to the upper and lower reference planes, and the chance of straycoupling between the line conductor and nearby objects is avoided. Inaddition to minimal radiation losses, a strip-line circuit's upper andlower ground planes may form a more efficient ground return path withless surface resistance than in the microstrip configuration.

An expression of the characteristic impedance, Z_(0sym), of a symmetric(balanced) strip-line, as shown in FIG. 1, is given by Equation 2. UsingEquation 2, for the signal trace 23 of width W_(C) and thickness T_(C),sandwiched by the PCB dielectric 21 of thickness T_(D) disposed betweenthe reference planes 22 and 24, the characteristic impedance Z_(0sym),of the symmetric strip-line 20 can be expressed as

$\begin{matrix}{{{Z_{0{sym}}(\Omega)} \approx {\frac{60}{\sqrt{ɛ_{r}}}\mspace{14mu}{\ln\left\lbrack \frac{4T_{D}}{\left( {0.67{\pi\left( {{0.8W_{C}} + T_{C}} \right)}} \right.} \right\rbrack}}},} & \left( {{Equation}\mspace{14mu} 2} \right)\end{matrix}$where ∈_(r) is the dielectric constant of the PCB dielectric 21.Equation 2 is generally valid for the following dimension ratios:W_(C)/(T_(D)−T_(C))<0.35 and T_(C)/B<0.25.

Microstrip and strip-line technologies are most commonly used routingconfigurations in circuits and can be used to provide well-characterizedtransmission line conductors that can be used to interconnect discretecircuit elements and to perform various impedance transformationfunctions. Strip-line transmission lines offer some electricalperformance advantages compared to microstrip, but strip-line is morecomplex to fabricate than microstrip. In high-frequency circuits, e.g.,microwave circuits, cost and/or space savings may be attained by usingstrip-line technology.

SUMMARY

A continuing need exists for methods of manufacturing strip-linecircuits with improved fabrication and assembly techniques. A continuingneed exists for strip-line configurations on printed circuit boards atlower costs. There is a need for methods of reducing the time,complexity and/or cost of strip-line fabrication operations and/orprinted circuit board inspection, test, and/or rework. There is a needfor methods of manufacturing printed circuit boards that allow access tocomponents assembled into strip-line configurations.

According to one aspect, a printed circuit board is provided. Theprinted circuit board includes a first layer stack and a second layerstack coupled to the first layer stack. The first layer stack includes afirst electrically-insulating layer, a first electrically-conductivelayer, and a cut-out area defining a void that extends therethrough. Thefirst electrically-insulating layer includes a first surface and anopposite second surface. The first electrically-conductive layer isdisposed on the first surface of the first electrically-insulatinglayer. The second layer stack includes a second electrically-insulatinglayer. The second electrically-insulating layer includes a first surfaceand an opposite second surface. The second layer stack may furtherinclude a second electrically-conductive layer disposed on the secondsurface of the second electrically-insulating layer. One or moreelectrically-conductive traces are disposed on the first surface of thesecond electrically-insulating layer. The printed circuit board furtherincludes a device at least partially disposed within the cut-out area.The device is electrically-coupled to at least one of the one or moreelectrically-conductive traces disposed on the first surface of thesecond electrically-insulating layer. The second layer stack may furtherinclude a second electrically-conductive layer disposed on the secondsurface of the second electrically-insulating layer.

According to one aspect, a multi-layer printed circuit board isprovided. The multi-layer printed circuit board includes a first layerstack and a second layer stack coupled to the first layer stack. Thefirst layer stack includes a first electrically-insulating layer, asecond electrically-insulating layer, and a firstelectrically-conductive layer disposed between the first and secondelectrically-insulating layers. The second layer includes a thirdelectrically-insulating layer and a second electrically-conductivelayer. The first layer stack and/or the second layer stack include acut-out area defining a void that extends therethrough. The multi-layerprinted circuit board further includes a first signal layer and a secondsignal layer. The first signal layer is disposed in association with thefirst electrically-insulating layer of the first layer stack or thethird electrically-insulating layer of the second layer stack. Thesecond signal layer is disposed in association with the secondelectrically-insulating layer of the first layer stack. The multi-layerprinted circuit board further includes a device at least partiallydisposed within the cut-out area. The device is electrically-coupled tothe first signal layer and/or the second signal layer.

In any one of the above aspects, the cut-out area may be configured toreceive therein at least a portion of the device. In any one of theabove aspects, the device includes a top surface of the device isdisposed below the second surface of the first electrically-conductivelayer. In any one of the above aspects, the printed circuit board ormulti-layer printed circuit board may further include a sheet ofelectrically-conductive material including a first portion configured tocover the cut-out area. The sheet of electrically-conductive materialmay further include a second portion disposed on at least a portion ofthe first surface of the first electrically-conductive layer.

In any one of the above aspects, an area of the first surface of thefirst electrically-insulating layer disposed adjacent to the cut-outarea is an exposed area. The printed circuit board or multi-layerprinted circuit board may further include a sheet ofelectrically-conductive material including a first portion and a secondportion, wherein the first portion is configured to cover the cut-outarea and the second portion is disposed on the exposed area of firstsurface of the first electrically-insulating layer.

According to a further aspect, a method of manufacturing a printedcircuit board is provided. The method includes the initial steps ofproviding a first layer stack and providing a second layer stack. Thefirst layer stack includes a first electrically-insulating layer. Thefirst electrically-insulating layer includes a first surface and one ormore electrically-conductive traces disposed on the first surface. Thesecond layer stack includes a second electrically-insulating layer and afirst electrically-conductive layer. The second electrically-insulatinglayer includes a first surface and an opposite second surface. The firstelectrically-conductive layer is disposed on the first surface of thesecond electrically-insulating layer. The second layer stack furtherincludes a cut-out area defining a void that extends therethrough. Thecut-out area is configured to receive therein at least a portion of adevice to be coupled to the first surface of the firstelectrically-insulating layer and/or electrically-coupled to one or moreof the one or more electrically-conductive traces. The first layer stackmay further include a second electrically-conductive layer disposed onthe second surface of the first electrically-insulating layer. Themethod may further include the step of coupling the first surface of thefirst electrically-insulating layer to the second surface of the secondelectrically-insulating layer. The coupling step may include the step oforienting the first layer stack and the second layer stack in relationto one another such that the first surface of the firstelectrically-insulating layer opposes the second surface of the secondelectrically-insulating layer. The coupling step may further include thestep of positioning the first layer stack and the second layer stack inrelation to one another such that the cut-out area is positioned toreceive the at least a portion of the device therein when the firstsurface of the first electrically-insulating layer is placed in contactwith the second surface of the second electrically-insulating layer. Thecoupling step may further include the step of bonding the secondelectrically-conductive layer of the third layer stack to the firstelectrically-insulating layer of the first layer stack.

The method may further include the step of mounting the device on thefirst layer stack. The mounting step may include the step of placing atleast a portion of the device within the cut-out area. The mounting stepmay further include the step of electrically-coupling the device to oneor more of the one or more electrically-conductive traces. The methodmay further include the step of coupling a third layer stack to thefirst layer stack. The third layer stack may include a signal layer anda third electrically-insulating layer including a first surface and anopposite second surface. The signal layer may be disposed in associationwith the first surface of the third electrically-insulating layer. Thethird layer stack may further include a second electrically-conductivelayer including a first surface and an opposite second surface, thefirst surface of the second electrically-conductive layer disposed onthe second surface of the third electrically-insulating layer.

According to a further aspect, a method of manufacturing a printedcircuit board is provided. The method includes the initial steps ofproviding a first layer stack including a first electrically-conductivelayer and a first electrically-insulating layer and providing a secondlayer stack including a second electrically-insulating layer. The firstelectrically-insulating layer a first surface and an opposite secondsurface. The first electrically-conductive layer is disposed on thefirst surface of the first electrically-insulating layer. The secondelectrically-insulating layer includes one or moreelectrically-conductive traces disposed on a first surface thereof. Themethod also includes the steps of mounting a device on the first surfaceof the second electrically-insulating layer such that the device iselectrically-coupled to at least one of the one or moreelectrically-conductive traces, and providing the first layer stack witha cut-out area defining a void that extends from the second surface ofthe first electrically-insulating layer to the first surface of thefirst electrically-conductive layer. The cut-out area is configured toreceive at least a portion of the device therein. The method alsoincludes the step of placing the first surface of the secondelectrically-insulating layer in contact with the second surface of thefirst electrically-insulating layer such that at least a portion of thedevice is disposed within at least a portion of the cut-out area.

According to a further aspect, a method of manufacturing a printedcircuit board is provided. The method includes the initial steps ofproviding a first electrically-insulating layer having a first surfaceand an opposite second surface, providing a firstelectrically-conductive layer on the first surface of the firstelectrically-insulating layer, and providing a cut-out area defining avoid that extends from the second surface of the firstelectrically-insulating layer to the first surface of the firstelectrically-conductive layer. The step of providing a firstelectrically-conductive layer on the first surface of the firstelectrically-insulating layer may include patterning, e.g.,photo-etching, the first electrically-conductive layer to provide anexposed area on the first surface of the first electrically-insulatinglayer disposed adjacent to the cut-out area. The method also includesthe steps of providing a second electrically-insulating layer having afirst surface and an opposite second surface, providing a secondelectrically-conductive layer on the second surface of the secondelectrically-insulating layer, providing one or moreelectrically-conductive traces on the first surface of the secondelectrically-insulating layer, mounting a device on the first surface ofthe second electrically-insulating layer such that the device iselectrically-coupled to at least one of the one or moreelectrically-conductive traces, and placing the second surface of thefirst electrically-insulating layer in contact with the first surface ofthe second electrically-insulating layer such that at least a portion ofthe device is disposed within at least a portion of the cut-out area.

In any one of the above aspects, the method of manufacturing a printedcircuit board may further include the steps of: determining whetherthere remains a volume of the void defined by the cut-out area above thedevice; if it is determined that there remains a volume of the voiddefined by the cut-out area above the device, then determining whetherthe volume of the void defined by the cut-out area above the device isto be at least partially filled with a dielectric material other than avacuum or a gas (or mixture of gases, such as air); and if it isdetermined that the volume of the void defined by the cut-out area abovethe device is to be at least partially filled with a dielectric materialother than a vacuum or a gas or a mixture of gases, then at leastpartially filling the volume of the void with the dielectric materialother than a vacuum or a gas or a mixture of gases.

In any one of the above aspects, the method of manufacturing a printedcircuit board may further include the steps of providing a sheet ofelectrically-conductive material including a first portion configured tocover the cut-out area when a second portion of the sheet ofelectrically-conductive material is disposed on the first surface of thefirst electrically-conductive layer, and coupling the second portion ofthe sheet of the electrically-conductive material to at least a portionof the first surface of the first electrically-conductive layer.

In any one of the above aspects, the method of manufacturing a printedcircuit board may further include the steps of providing a thirdelectrically-insulating layer having a first surface and an oppositesecond surface, placing the second surface of the thirdelectrically-insulating layer in contact with one of the first surfaceof the first electrically-conductive layer and the first surface of thesecond electrically-conductive layer, and providing one or moreelectrically-conductive traces on the first surface of the thirdelectrically-insulating layer.

In any one of the above aspects, the method of manufacturing a printedcircuit board may further include the steps of providing a thirdelectrically-insulating layer having a first surface and an oppositesecond surface, placing the second surface of the thirdelectrically-insulating layer in contact with the first surface of thesecond electrically-conductive layer, and providing one or moreelectrically-conductive traces on the first surface of the thirdelectrically-insulating layer.

According to a further aspect, a method of manufacturing a printedcircuit board is provided. The method includes the initial step ofproviding first and second layer stacks. The first layer stack includesa first electrically-conductive layer. The first layer stack furtherincludes first and third electrically-insulating layers disposed onopposite sides of the first electrically-conductive layer. The secondlayer stack includes a second electrically-insulating layer having afirst surface and an opposite second surface. The second layer stackfurther includes a second electrically-conductive layer disposed on thesecond surface of the second electrically-insulating layer. The methodfurther includes the steps of providing a device on the first surface ofthe second electrically-insulating layer such that the device iselectrically-coupled to at least one of one or moreelectrically-conductive traces disposed on the first surface of thesecond electrically-insulating layer, and providing the first layerstack with a cut-out area defining a void that extends from an outersurface of the first electrically-insulating layer to an outer surfaceof third electrically-insulating layer. The cut-out area is configuredto receive at least a portion of the device therein. The method mayfurther include the step of placing the first surface of the secondelectrically-insulating layer in contact with the outer surface of thefirst electrically-insulating layer such that at least a portion of thedevice is disposed within at least a portion of the cut-out area.

The method may further include the step of providing a pattern of one ormore electrically-conductive traces on one or more areas of the outersurface of the third electrically-insulating layer. The one or moreareas are spaced apart from the cut-out area. The method may furtherinclude the step of providing one or more devices on the outer surfaceof the third electrically-insulating layer such that at least one of theone or more devices is electrically-coupled to at least one of the oneor more electrically-conductive traces disposed on the outer surface ofthe third electrically-insulating layer.

In any one of the above aspects, the cut-out area may be configured toreceive therein at least a portion of the device. In any one of theabove aspects, the height of the device may be less than the thicknessof the first electrically-insulating layer. In any one of the aboveaspects, the device may include a top surface and a bottom surface. Inany one of the above aspects, the top surface of the device may bedisposed below the second surface of the first electrically-conductivelayer. In any one of the above aspects, the height of the device may begreater than the height of the first layer stack.

In any one of the above aspects, the printed circuit board may furtherinclude a sheet of electrically-conductive material configured to coverthe cut-out area. The sheet of electrically-conductive material mayinclude a first portion configured to cover the cut-out area and asecond portion disposed on at least a portion of the first surface ofthe first electrically-conductive layer.

In any one of the above aspects, an area of the first surface of thefirst electrically-insulating layer disposed adjacent to the cut-outarea may be an exposed area. In any one of the above aspects, the sheetof electrically-conductive material includes a first portion configuredto cover the cut-out area and a second portion disposed on the exposedarea of first surface of the first electrically-insulating layer.

In any one of the above aspects, the printed circuit board may furtherinclude one or more gap areas disposed in adjoining relation to thecut-out area. The one or more gap areas may be configured to physicallyisolate the device from the first electrically-conductive layer and/orelectrically isolate the device from the first electrically-conductivelayer.

In any one of the above aspects, the printed circuit board may furtherinclude a heat sink disposed in association with the top surface of thedevice.

In any one of the above aspects, the void defined by the cut-out areamay include a first volume of void space defined between the top surfaceof the device and a plane containing the first surface of the firstelectrically-conductive layer. The printed circuit board may furtherinclude dielectric material disposed in at least a portion of the firstvolume of void space.

In any one of the above aspects, the printed circuit board may furtherinclude a sheet of electrically-conductive material configured to coverthe cut-out area.

In any one of the above aspects, the printed circuit board may furtherinclude a third layer stack coupled to the first layer stack, the thirdlayer stack including a third electrically-insulating layer having afirst surface. The printed circuit board may further include a signallayer disposed in association with the first surface of the thirdelectrically-insulating layer. The printed circuit board may furtherinclude a cut-out area defining a void that extends from the firstsurface of the third electrically-insulating layer to first surface ofthe second electrically-insulating layer.

BRIEF DESCRIPTION OF THE DRAWINGS

Objects and features of the presently-disclosed printed circuit boardsincluding strip-line circuitry and methods of manufacturing the samewill become apparent to those of ordinary skill in the art whendescriptions of various embodiments thereof are read with reference tothe accompanying drawings, of which:

FIG. 1 is an enlarged, cross-sectional view of a printed circuit board(PCB) having a microstrip transmission line according to a conventionaltechnology;

FIG. 2 is an enlarged, cross-sectional view of a PCB having a symmetricstrip-line transmission line according to a conventional technology;

FIG. 3 is an enlarged, perspective, cross-sectional view of a portion ofa PCB with layer stacks separated including a cut-out area defined in afirst layer stack according to an embodiment of the present disclosure;

FIG. 4 is an enlarged, perspective, cross-sectional view of the PCB ofFIG. 3 shown assembled with a device disposed in a first-levelconfiguration within the cut-out area according to an embodiment of thepresent disclosure;

FIG. 5 is an enlarged, cross-sectional view of a PCB including anasymmetric strip-line transmission line according to an embodiment ofthe present disclosure;

FIG. 6 is an enlarged, perspective, cross-sectional view of anembodiment of a first layer stack including the cut-out area of the PCBshown in FIG. 3 defined therethrough shown with a configuration of gapareas disposed along two opposite sides of the cut-out area according tothe present disclosure;

FIG. 7 is an enlarged, perspective, cross-sectional view of anembodiment of a first layer stack including the cut-out area of the PCBshown in FIG. 3 defined therethrough shown with a configuration of gapareas disposed around the outer periphery of the cut-out area accordingto the present disclosure;

FIG. 8 is an enlarged, perspective, cross-sectional view of a portion ofa PCB including the first layer stack of FIG. 6 and the second layerstack of FIG. 3 shown assembled with a device disposed in a first-levelconfiguration within the cut-out area according to an embodiment of thepresent disclosure;

FIG. 9 is an enlarged, perspective, cross-sectional view of a portion ofa PCB including the first layer stack of FIG. 7 and the second layerstack of FIG. 3 shown assembled with a device disposed in a first-levelconfiguration within the cut-out area according to an embodiment of thepresent disclosure;

FIG. 10A is an enlarged, perspective, cross-sectional view of a portionof a PCB with layer stacks separated that includes the first layer stackof FIG. 7 shown with the cut-out and gap areas defined therethrough andthe second layer stack of FIG. 3 shown with a portion of a conductorline disposed thereon according to an embodiment of the presentdisclosure;

FIG. 10B is an enlarged, perspective, cross-sectional view of the PCB ofFIG. 10A shown with a device positioned for placement onto the secondlayer stack through the cut-out area of the first layer stack accordingto an embodiment of the present disclosure;

FIG. 10C is an enlarged, perspective, cross-sectional view of the PCB ofFIG. 10B shown assembled with a device disposed in a second-levelconfiguration within the cut-out area according to an embodiment of thepresent disclosure;

FIG. 11 is an enlarged, perspective, cross-sectional view of the PCB ofFIG. 10C shown with a portion of a heat sink layer according to anembodiment of the present disclosure;

FIG. 12 is an enlarged, perspective, cross-sectional view of a portionof a PCB with layer stacks separated including another embodiment of afirst layer stack including a cut-out area defined therethrough and thesecond layer stack of FIG. 3 according to the present disclosure;

FIG. 13 is an enlarged, perspective, cross-sectional view of a portionof a PCB with layer stacks separated including a first cut-out areadefined in a first layer stack and a second cut-out area defined in asecond layer stack according to an embodiment of the present disclosure;

FIG. 14 is an enlarged, perspective, cross-sectional view of a portionof a PCB with layer stacks separated including the first layer stack ofFIG. 13 and another embodiment of a second layer stack including acut-out area defined therethrough according to the present disclosure;

FIG. 15 is a schematic, enlarged, perspective view of a portion of a PCBaccording to another embodiment of the present disclosure;

FIG. 16A is an enlarged, cross-sectional view taken along section lines16A-16A of FIG. 15;

FIG. 16B is an enlarged, cross-sectional view of an alternativeembodiment of the PCB shown in FIGS. 15 and 16A according to the presentdisclosure;

FIG. 17 is an enlarged, cross-sectional view of a portion of a PCBaccording to yet another embodiment of the present disclosure;

FIG. 18 is a flowchart illustrating a method of manufacturing a PCB inaccordance with an embodiment of the present disclosure;

FIG. 19 is a flowchart illustrating a method of manufacturing a PCB inaccordance with an embodiment of the present disclosure;

FIG. 20 is a flowchart illustrating a method of manufacturing a PCB inaccordance with another embodiment of the present disclosure;

FIG. 21 is a flowchart illustrating a method of manufacturing a PCB inaccordance with another embodiment of the present disclosure;

FIG. 22 is a flowchart illustrating a method of manufacturing a PCB inaccordance with yet another embodiment of the present disclosure;

FIG. 23 is a flowchart illustrating a method of manufacturing a PCB inaccordance with yet another embodiment of the present disclosure;

FIG. 24 is a flowchart illustrating a method of manufacturing a PCB inaccordance with yet another embodiment of the present disclosure;

FIG. 25 is a flowchart illustrating a method of manufacturing a PCB inaccordance with still another embodiment of the present disclosure; and

FIG. 26 is a flowchart illustrating a method of manufacturing a PCB inaccordance with still another embodiment of the present disclosure.

DETAILED DESCRIPTION

Hereinafter, embodiments of the presently-disclosed printed circuitboards including strip-line circuitry and methods of manufacturing thesame are described with reference to the accompanying drawings. Likereference numerals may refer to similar or identical elements throughoutthe description of the figures. As shown in the drawings and as used inthis description, and as is traditional when referring to relativepositioning on an object, the term “proximal” refers to that portion ofthe device, or component thereof, closer to the user and the term“distal” refers to that portion of the device, or component thereof,farther from the user.

This description may use the phrases “in an embodiment,” “inembodiments,” “in some embodiments,” or “in other embodiments,” whichmay each refer to one or more of the same or different embodiments inaccordance with the present disclosure. For the purposes of thisdescription, a phrase in the form “A/B” means A or B. For the purposesof the description, a phrase in the form “A and/or B” means “(A), (B),or (A and B)”.

As it is used in this description, “printed circuit board” (or “PCB”) or“circuit boards” generally refers to systems that provide, among otherthings, mechanical support to electrical devices and/or components,electrical connection to and between these electrical devices and/orcomponents, combinations thereof, and the like. For the purposes herein,the term “printed circuit board” is interchangeable with the term“printed wiring board” and either is represented herein by the acronymPCB. The PCBs described herein may include electrical components. Ingeneral, the term “printed circuit board” is interchangeable, in thisdisclosure, with the terms “printed circuit assembly” and “printedcircuit board assembly”. The PCBs and circuit boards described hereinare not limited to electrical component-populated boards, but alsoinclude non-populated circuit-traced substrates of all types.

PCB embodiments described herein include one or more layer stacks formedof a plurality of layers of suitable electrically-conductive and/ornon-conductive materials. Examples of suitable materials may include,without limitation, dielectrics, e.g., polytetrafluoroethylene(Teflon®), FR-4 (flame retardant 4), CEM-1 or CEM-3, low-loss dielectricPCB material, e.g., Rogers 4350, GETEK® or ARLON,electrically-conductive materials such as without limitation metal,e.g., copper foil, fibrous materials, e.g., carbon, graphite, graphene,glass, quartz, polyethylene or liquid crystal polymer fibers, prepregmaterials, e.g., FR-2 (phenolic cotton paper), FR-3 (cotton paper andepoxy), FR-4 (woven glass and epoxy), FR-5 (woven glass and epoxy), FR-6(matte glass and polyester), G-10 (woven glass and epoxy), CEM-1 (cottonpaper and epoxy), CEM-2 (cotton paper and epoxy), CEM-3 (woven glass andepoxy), CEM-4 (woven glass and epoxy) or CEM-5 (woven glass andpolyester), or other suitable electrically-conductive or non-conductivematerials, e.g., fibrous materials with low coefficients of thermalexpansion that are metalized to provide a resultantelectrically-conductive material with a low coefficient of thermalexpansion.

As it is used in this description, “electrically conductive”, or simply“conductive”, generally refers to materials that are capable ofelectrical conductivity, including, without limitation, materials thatare highly conductive, e.g., metals, or semi-conductive, e.g.,semi-conducting materials and composites As it is used in thisdescription, “ground plane” refers to not only conductive planes whichin operation are coupled to ground potential, but also conductive planesthat may be coupled to other circuit potentials. Generally speaking, aground plane is a relatively large plane of material having lowelectrical impedance. In implementations, it may actually be either aground plane or a power plane (commonly referred to as referenceplanes).

Various embodiments of the presently-disclosed PCBs include at least onelayer stack that includes an electrically-conductive layer (e.g., aground plane or a power plane), an electrically-insulating layer (alsoreferred to herein as an “insulative layer”) and one or more cut-outareas defining a void that extends therethrough. In embodiments of thepresently-disclosed PCBs, a variety of electrically-conductive traces(e.g., strip-line traces, microstrip traces, embedded microstrip traces,and/or combinations thereof) may be used in conjunction with one or morepower planes to form transmission lines.

The presently-disclosed PCBs according to embodiments may be multi-layerPCBs that employ a variety of transmission lines, including, withoutlimitation, strip-line configurations on internal layers of the PCB,e.g., providing power distribution, digital signal processing, and otherfunctions, and/or microstrip configurations on external layers of thePCB.

Various embodiments of the presently-disclosed PCBs include one or morecut-out areas defined in at least one layer stack, and may providestrip-line shielding capability along with microstrip-like accessibilityto add components on and off the circuit board and/or to perform otheroperations, e.g., testing. The presently-disclosed PCBs including one ormore cut-out areas defined in one or more layer stacks may provide thecapability to add or remove component capacitance to equalize the line.

Although the following description describes the use of symmetric(balanced) strip-line construction in PCB embodiments including one ormore cut-out areas defined in one or more layer stacks, the teachings ofthe present disclosure may also apply to asymmetric or offset(unbalanced) strip-line routing. A PCB embodiment that includes anasymmetric strip-line transmission line is shown in the cross-sectionalview of FIG. 5. A multi-layer PCB embodiment including an asymmetricstrip-line configuration is shown in FIG. 17.

FIG. 3 shows a portion of a PCB 100 with first and second layer stacksseparated according to an embodiment of the present disclosure. PCB 100includes a first layer stack 102 and a second layer stack 104. Firstlayer stack 102 includes a cut-out area 130 defined therethrough.Although only one cut-out area 130 is shown in FIG. 3 for ease ofillustration, it is to be understood that PCB 100 may include any numberof cut-out areas defined in the first layer stack 102 and/or the secondlayer stack 104. As shown in FIG. 3, the first layer stack 102 has aheight “H₁”. Height “H₁” may be any suitable height. First layer stack102 generally includes a first conductive layer 110 and a firstinsulative layer 120 upon which the first conductive layer 110 issupported. In some embodiments, the first conductive layer 110 may beeither a power plane or a ground plane.

Second layer stack 104 includes a second insulative layer 140. Firstinsulative layer 120 and the second insulative layer 140 may include anysuitable material configured to resist, or substantially resist, theflow of electricity and to provide physical support for, among otherthings, one or more conductive layers, electrical and/or electroniccomponents, devices, connectors, etc. In some embodiments, the firstinsulative layer 120 and/or the second insulative layer 140 may includeone or more layers of dielectric laminate.

As shown in FIG. 3, the first conductive layer 110 generally includes afirst surface 111 and an opposite second surface 112. First conductivelayer 110 may include a single layer or multiple layers disposed betweenthe first and second surfaces 111 and 112, respectively. Secondconductive layer 150 generally includes a first surface 151 and anopposite second surface 152. Second conductive layer 150 may include asingle layer, or a plurality of layers, disposed between the first andsecond surfaces 151 and 152, respectively.

First insulative layer 120 generally includes a first surface 121 and anopposite second surface 122. First insulative layer 120 may include asingle layer, or a plurality of layers, disposed between the first andsecond surfaces 121 and 122, respectively. First insulative layer 120may have any suitable thickness “T_(D1)”. Height “H₂” of the device 170may be less than the thickness “T_(D1)” of the first insulative layer120.

In some embodiments, the first conductive layer 110 may be depositeddirectly on, or coupled to, the first surface 121 of the firstinsulative layer 120. Alternatively, one or more layers (not shown) maybe disposed between the second surface 112 of the first conductive layer110 and the first surface 121 of the first insulative layer 120. In analternative embodiment not shown, a sheet of thermally-responsivematerial may be disposed between the first surface 121 of the firstinsulative layer 120 and the second surface 112 of the first conductivelayer 110, e.g., to form a laminated bond therebetween. In someembodiments, the first conductive layer 110 and the first insulativelayer 120 are arranged in substantially parallel planes.

In some embodiments, as shown in FIG. 3, a second conductive layer 150and a circuit 176 are disposed on opposite sides of the secondinsulative layer 140. In some embodiments, the second conductive layer150 may be either a power plane or a ground plane. Circuit 176 generallyincludes a device 170 and one or more electrically-conductive traces 160disposed on the second insulative layer 140. Circuit 176 may include acollection of circuit elements, e.g., transistors, diodes, capacitors,and resistors, as well as signal lines and other conductors thatinterconnect these various circuit elements. Conductive traces 160 havea controlled width “W_(C)” and a thickness “T_(C)”, and may be formed ofany suitable electrically-conductive material, e.g., copper, gold,silver or other conductive metals having suitable conductivity values.Conductive traces of the circuit 176 may be characterized by a firstwidth “W_(C1)” of an upper surface thereof and a second width “W_(C2)”of a lower surface, as shown in FIG. 5.

Device 170 may be electrically-coupled to one or more conductive traces160. Device 170 may include any electrical device, electrical component,electronic device, electronic component, semiconductor component, etc.Device 170 may include any electrical connector, such as withoutlimitation surface mount connectors in SMA, SMB, SMC, SSMB, and SSMC. Insome embodiments, multiple electrical components may be assembled intothe device 170, which itself may be used as a component. Device 170 mayinclude active devices and/or passive devices. In some embodiments, thedevice 170 may be a capacitor.

Device 170 generally includes a top surface 171 and a bottom surface173. Device 170 includes a height “H₂” defined between the top andbottom surfaces 171 and 173, respectively. Height “H₂” may be anysuitable height. In some embodiments, the height “H₂” of the device 170is less than the height “H₁” of the first layer stack 102. Device 170may take a variety of shapes and sizes. For ease of explanation andunderstanding, the device 170 is shown as a single element having arectangular shape.

First conductive layer 110 and the second conductive layer 150 may beformed of any suitable electrically-conductive material, e.g., copper,gold, silver or other conductive metals having suitable conductivityvalues. In some embodiments, the first conductive layer 110 and/or thesecond conductive layer 150 may be a conductive foil. Conductivematerials that may be used to form the first conductive layer 110 and/orthe second conductive layer 150 may be plated with other materials,e.g., other conductive materials such as gold or silver, to improvetheir properties, e.g., to improve electrical conductivity.

Second insulative layer 140 generally includes a first surface 141 andan opposite second surface 142. Second insulative layer 140 may includea single layer or multiple layers disposed between the first and secondsurfaces 141 and 142, respectively. Second insulative layer 140 may haveany suitable thickness “T_(D2)”. In some embodiments, the firstinsulative layer 120 is formed from a material with a dielectricconstant different than the dielectric constant of the second insulativelayer 140.

In some embodiments, the thickness “T_(D1)” of the first insulativelayer 120 of the first layer stack 102 may be substantially equal to thethickness “T_(D2)” of the second insulative layer 140 of the secondlayer stack 104. Alternatively, the thickness “T_(D1)” of the firstinsulative layer 120 may be less than, or greater than, the thickness“T_(D2)” of the second insulative layer 140.

As best shown in FIG. 3, the first layer stack 102 includes a cut-outarea 130 defining a void that extends from the second surface 122 of thefirst insulative layer 120 to the first surface 111 of the firstconductive layer 110. The height of the cut-out area 130 is generallyequal to the height “H₁” of the first layer stack 102. Cut-out area 130according to embodiments is configured to receive at least a portion ofthe device 170 therein. Cut-out area 130 may take a variety of shapesand sizes.

In some embodiments, the void defined by the cut-out area 130 mayinclude a first volume “V₁” of void space and a second volume “V₂” ofvoid space. The first volume “V₁” of void space is defined between thetop surface 171 of the device 130 and a plane (depicted by arrow-headeddotted lines in FIG. 4) containing the first surface 111 of the firstelectrically-conductive layer 110. The second volume “V₂” of void spaceis equal to the volume of the device 130, or portion thereof, to bedisposed within the cut-out area 130.

In FIG. 4, an assembled configuration of the PCB 100 is shown andincludes the first layer stack 102 including the cut-out area 130defined therethrough and the second layer stack 104 with the device 170disposed in a first-level configuration within the cut-out area 130. Asit is used in this description, with respect to the cut-out area 130,“first-level configuration” generally refers to varied configurationswherein the top surface 171 of the device 170 is disposed (e.g., inrelation to the first conductive layer 110) below the level of thesecond surface 112 of the first conductive layer 110, such that theperipheral edges of the device 170 do not physically contact the firstconductive layer 110. In other PCB embodiments, “first-levelconfiguration” may be used in the context of other devices (e.g., device1070 shown in FIGS. 10B, 10C and 11, and device 1370 shown in FIGS. 13and 14).

In some embodiments, a dielectric material 180 (shown in FIG. 3) may beused to fill, entirely or in part, a volume of void space defined by thecut-out area 130 disposed above (e.g., extending outwardly from) the topsurface 171 of the device 170. Dielectric material 180 may be anysuitable material having any suitable dielectric constant.

Cut-out areas in accordance with the present disclosure (e.g., onecut-out area 130 shown in FIG. 3, or two cut-out areas 1303 and 1330shown in FIG. 13) may be formed by any suitable process, e.g., lasercutting, stamping, punching and/or die-cutting, or any combination ofthese and other processes, e.g., photo-etching. In some embodiments, oneor more cut-out areas may be formed by fineblanking, or a combination offineblanking and forming operations.

Fineblanking may be used to achieve flatness and cut edgecharacteristics that may be unobtainable by conventional stamping andpunching methods. In general, fineblanking operations require the use ofhigh-pressure pads and are carried out on triple-action hydraulicpresses on which the punch, guide plate, and die movements can becontrolled individually or simultaneously. The pads hold the part flatduring the cutting process and prevent the part from plasticallydeforming during punch entry. Using fineblanking, a part's cut surfaceis sheared smoothly over the entire workpiece thickness, with minimaldie roll on edges. Achievable part dimensional tolerances may range fromabout +/−0.0003 inches to about +/−0.002 inches, depending upon materialthickness, material characteristics (e.g., tensile strength), and partlayout. The use of fineblanking processes allows excellent dimensionalcontrol, accuracy and repeatability throughout a production run.

In some embodiments, the cut-out area 130 may be characterized asincluding an outer periphery having a length and a width that is atleast marginally larger than the length and width, respectively, of thedevice 170, e.g., to allow for ease of assembly of the PCB 100. In someembodiments, one or more surfaces of the first insulative layer 120(and/or first conductive layer 110) disposed adjacent to the outerperiphery of the cut-out area 130 may include one or more grooves,slots, pockets, channels or other recesses configured to accommodate andreceive therein one or more portions of a device, and/or to allow forair circulation around the device, or portion thereof, to increase heatdissipation. Additionally, or alternatively, a configuration of gapareas, which are described later in this description, may be provided tothe first layer stack 102, e.g., disposed in adjoining relation to thecut-out area 130, or portion thereof.

In some embodiments, the first electrically-conductive layer 110 of thefirst stack 102 may be formed, patterned or otherwise deposited on thesurface of first insulative layer 120 to avoid or otherwise exclude oneor more areas 113 disposed adjacent to the outer periphery of thecut-out area 130. Alternatively, one or more areas 113 of the surface offirst insulative layer 120 may be exposed by removal of one or moreportions of the first electrically-conductive layer 110.

As shown in FIG. 3, a sheet of electrically-conductive material 190 maybe provided, and may include a first portion 194 configured to cover thecut-out area 130 when a second portion 195 of the sheet 190 is disposedon either, the first surface 111 of the first conductive layer 110, orthe first surface 121 of the first insulative layer 120.Electrically-conductive material 190 may include various types ofmaterials in varied configurations, including, without limitation, aconductive tape (e.g., carbon conductive tape or copper conductive tape)or a conductive adhesive sheet (e.g., silver conductive adhesive sheet).In some embodiments, the sheet of electrically-conductive material 190,or portion thereof (e.g., second portion 195), may be provided with asuitable adhesive material for affixing, permanently or releaseably, thesheet of electrically-conductive material 190, or portion thereof, tothe first surface 111 of the first conductive layer 110 and/or the firstsurface 121 of the first insulative layer 120.

FIG. 5 shows a PCB 500 that includes an asymmetric strip-linetransmission line according to an embodiment of the present disclosure.PCB 500 includes a first layer stack 502 and a second layer stack 504.First layer stack 502 includes a first conductive layer 510 and a firstinsulative layer 520 upon which the first conductive layer 510 issupported. Second layer stack 504 includes a second conductive layer 550and a second insulative layer 540. An electrically-conductive trace 560is sandwiched by the first and second insulative layers 520 and 540disposed between the first and second conductive layers 510 and 550.First conductive layer 510 and second conductive layer 550 are similarto the first conductive layer 110 and the second conductive layer 150,respectively, shown in FIG. 3 and further description thereof is omittedin the interests of brevity.

First insulative layer 520 and the second portion second insulativelayer 540 are similar to the first insulative layer 120 and the secondinsulative layer 140, respectively, of PCB 100 shown in FIG. 3, exceptfor the thickness of the first insulative layer 520 in relation to thethickness of the second insulative layer 540. As shown in FIG. 5, thethickness “T_(D3)” of the first insulative layer 520 is less than thethickness “T_(D4)” of the second insulative layer 540.Electrically-conductive trace 560 may be disposed on the secondinsulative layer 540. Electrically-conductive trace 560 generallyincludes a thickness “T_(C)”, an upper surface having a width “W_(C1)”,and a lower surface having a width “W_(C2)”.

FIG. 6 shows an embodiment of a first layer stack 602 including acut-out area 130 defined therethrough in accordance with the presentdisclosure. First layer stack 602 generally includes the firstconductive layer 110 and the first insulative layer 120 of the firstlayer stack 102 shown in FIG. 3. First layer stack 602 may have anysuitable height “H₁”.

First layer stack 602 is similar to the first layer stack 102 shown inFIG. 3, except for a configuration of gap areas disposed along twoopposite sides of the cut-out area 130, e.g., to simplify physicalinterconnections and assembly operations (e.g., component placement andsoldering) and/or to facilitate inspection and test. As shown in FIGS. 6and 8, the first layer stack 602 includes a first gap area 632 and asecond gap area 634. First and second gap areas 632 and 634 disposedalong two opposite sides of the cut-out area 130 may be configured toallow for removal of the device 170, e.g., to facilitate the replacementof parts and/or hardware upgrade, and/or to allow for air circulationfor heat dissipation purposes. The shape, size and relative positions ofthe first and second gap areas 632 and 634, respectively, may be variedfrom the configuration depicted in FIGS. 6 and 8.

FIG. 7 shows an embodiment of a first layer stack 702 including acut-out area 130 defined therethrough in accordance with the presentdisclosure. First layer stack 702 generally includes the firstconductive layer 110 and the first insulative layer 120 of the firstlayer stack 102 shown in FIG. 3. First layer stack 702 may have anysuitable height “H₁”.

First layer stack 702 is similar to the first layer stack 102 of PCB 100shown in FIG. 3, except for a gap area disposed in association with thecut-out area 130. As shown in FIGS. 7 and 9, the first layer stack 702includes a gap area 736 disposed around the outer periphery of thecut-out area 130, e.g., to optimize ease and economy of assembly,inspection, test, and acceptance of components, and/or to enhanceelectrical isolation of the device 170 from the first conductive layer110. The shape and size of the gap area 736 may be varied from theconfiguration depicted in FIGS. 7 and 9.

FIG. 8 shows a portion of a PCB 800 according to an embodiment of thepresent disclosure. In FIG. 8, the first layer stack 602 of FIG. 6including the cut-out area 130 defined therethrough and the second layerstack 104 of FIG. 3 are shown assembled with the device 170 disposed ina first-level configuration within the cut-out area 130.

FIG. 9 shows a portion of a PCB 900 according to an embodiment of thepresent disclosure. In FIG. 9, the first layer stack 702 of FIG. 7including the cut-out area 130 defined therethrough and the second layerstack 104 of FIG. 3 are shown assembled with the device 170 disposed ina first-level configuration within the cut-out area 130.

FIG. 10A shows a portion of a PCB 1000 with first and second layerstacks separated according to an embodiment of the present disclosure.PCB 1000 generally includes the first layer stack 702 of FIG. 7 and thesecond layer stack 104 of FIG. 3. First layer stack 702 has any suitableheight “H₁”. First layer stack 702 includes the cut-out area 130 definedtherethrough and the gap area 736 surrounding the cut-out area 130. Oneor more electrically-conductive traces 160 are disposed (e.g., formed,patterned or otherwise deposited) on the second insulative layer 140 ofthe second layer stack 104. Second layer stack 104 has any suitableheight “H₃”.

In FIG. 10B, the first layer stack 702 and second layer stack 104 areshown assembled with a device 1070 positioned above the first layerstack 702 for placement into the cut-out area 130 onto the second layerstack 104 according to an embodiment of the present disclosure. Device1070 generally includes a top surface 1071 and a bottom surface 1073.Device 1070 includes a height “H₅” defined between the top and bottomsurfaces 1071 and 1073, respectively. Height “H₅” may be any suitableheight.

Device 1070 shown in FIGS. 10B and 10C is similar to the device 170 ofFIG. 3, except for the height “H₅” of the device 1070, which is greaterthan the height “H₃” of the device 170 of FIG. 3, by a height “H₄”.Device 1070 may take a variety of shapes and sizes. In some embodiments,the device 1070 may be mounted, or otherwise disposed on, or adjacentto, the second insulative layer 140 of the second layer stack 104.Device 1070 may be electrically-coupled to one or moreelectrically-conductive traces 160 disposed in association with thesecond insulative layer 140.

In FIG. 10C, the PCB 1000 of FIG. 10B is shown with the device 1070disposed in a second-level configuration. As it is used in thisdescription, “second-level configuration”, with respect to the device1070, generally refers to varied configurations wherein a first portionof the device 1070 is disposed within a cut-out area (e.g., cut-out area1303 shown in FIGS. 13 and 14) and a second portion including the topsurface 1071 is disposed (e.g., in relation to the first conductivelayer 110) outwardly of the first surface 111 and/or the second surface112 of the first conductive layer 110. In other PCB embodiments,“second-level configuration” may be used with respect to other devices(e.g., device 170 shown in FIGS. 3, 4, 8, 9, 12, 13, 14 and 15, device1070 shown in FIGS. 10B, 100 and 11, and device 1370 shown in FIGS. 13and 14).

As shown in FIG. 100, the top surface 1071 of the device 1070 extends aheight “H₄” above the first surface 111 of the first conductive layer110, wherein the gap area 736 is configured such that the peripheraledges of the device 1070 do not physically contact the first conductivelayer 110, e.g., to electrically isolate the device 1070 from the firstconductive layer 110.

FIG. 11 shows a PCB 1100 according to an embodiment of the presentdisclosure that includes the PCB 1000 shown in FIG. 10C. PCB 1100includes, or is otherwise associated with, a heat sink 1185. Heat sink1185 may include one or more heat transfer layers capable of absorbingheat from an object. Heat sink 1185 may be a fluid-cooled heat sink.Heat sink 1185 may include integral sensing elements, and may be used aspart of a system to provide a controlled temperature to one or moredevices (e.g., device 1070 shown in FIG. 11).

As shown in FIG. 11, at least a portion of the heat sink 1185 isdisposed in association with the top surface 1071 of the device 1070. Insome embodiments, the heat sink 1185, or portion thereof, may bedisposed on a portion of the top surface 1071, or relatively near thetop surface 1071 of the device 1070.

FIG. 12 shows a portion of a PCB 1200 with first and second layer stacksseparated according to an embodiment of the present disclosure. PCB 1200includes a first layer stack 1202 and the second layer stack 104 shownin FIG. 3. First layer stack 1202 has a height “H₆” and generallyincludes a first conductive layer 1210, a first insulative layer 1220, aprepreg layer 1225, and a cut-out area 1203 defined therethrough. Firstlayer stack 1202 may have any suitable height “H₆”. First conductivelayer 1210 is similar to the first conductive layer 110 shown in FIG. 3and further description thereof is omitted in the interests of brevity.

First insulative layer 1220 may be formed from any suitable dielectricor insulating material. First insulative layer 1220 generally includes afirst surface 1221 and an opposite second surface 1222. First insulativelayer 1220 may include a single layer or multiple layers disposedbetween the first and second surfaces 1221 and 1222, respectively. Firstinsulative layer 1220 may have any suitable thickness “T_(D5)”. In someembodiments, the first insulative layer 1220 of the first layer stack1202 is formed from a material with a dielectric constant different thanthe dielectric constant of the second insulative layer 140 of the secondlayer stack 104. In some embodiments, the height “H₆” of the first layerstack 1202 may be substantially equal to the height “H₃” of the secondlayer stack 104.

Prepreg layer 1225 has a thickness “T_(D6)” and generally includes afirst surface 1227 and an opposite second surface 1226. In someembodiments, as shown in FIG. 12, the first surface 1227 of the prepreglayer 1225 is coupled to the second surface 1222 of the first insulativelayer 1220 of the first layer stack 1202. In an alternative embodimentnot shown, a prepreg layer may additionally, or alternatively, becoupled to the first surface 141 of the second insulative layer 120 ofthe second layer stack 104. Thickness “T_(D6)” may be any suitablethickness.

Prepreg layer 1225 may be formed from any suitable material. In someembodiments, the prepreg layer 1225 may include one or more layers ofFR-2, FR-3, FR-4, FR-5, FR-6, G-10, CEM-1, CEM-2, CEM-3, CEM-4, CEM-5,and/or any suitable epoxy resin composition, fiber-reinforced compositematerial, and/or other suitable material disposed between the first andsecond surfaces 1227 and 1226, respectively.

FIG. 13 shows a portion of a PCB 1300 with first and second layer stacksseparated according to an embodiment of the present disclosure. PCB 1300includes a first cut-out area 1303 defined in a first layer stack 1302,and a second cut-out area 1330 defined in a second layer stack 1304.Although only two cut-out areas 1303 and 1330 are shown in FIG. 13 forease of illustration, it is to be understood that PCB 1300 may includeany number of cut-out areas defined in the first layer stack 1302 and/orthe second layer stack 1304.

First layer stack 1302 includes the first conductive layer 110 and thefirst insulative layer 120 shown in FIG. 3. First conductive layer 110includes a first surface 111 and an opposite second surface 112. Firstinsulative layer 120 includes a first surface 121 and an opposite secondsurface 122. In some embodiments, the first conductive layer 110 may beeither a power plane or a ground plane.

As shown in FIG. 13, a circuit 1376 is disposed in association with thesecond surface 122 of the first insulative layer 120 of the first layerstack 1302. Circuit 1376 generally includes a device 1370 and one ormore electrically-conductive traces 1360 disposed (e.g., formed,patterned, or otherwise deposited) on the second surface 122 of thefirst insulative layer 120. Circuit 1376 is similar to the circuit 176shown in FIG. 3 and further description thereof is omitted in theinterests of brevity.

Second layer stack 1304 includes a second insulative layer 1340. Secondinsulative layer 1340 generally includes a first surface 1341 and anopposite second surface 1342. Second insulative layer 1340 may include asingle layer, or a plurality of layers, of any suitable dielectric orinsulating material disposed between the first and second surfaces 1341and 1342, respectively. Circuit 176 is disposed in association with thefirst surface 1341 of the second insulative layer 1340. In someembodiments, as shown in FIG. 13, a second conductive layer 1350 issupported by the second surface 1342 of the second insulative layer1340. Second conductive layer 1350 generally includes a first surface1351 and an opposite second surface 1352. In an alternative embodimentnot shown, one or more layers of any suitable material may be disposedbetween the second surface 1342 of the second insulative layer 1340 andthe second surface 1352 of the second conductive layer 1350, e.g., toform a bond therebetween. In some embodiments, the second conductivelayer 1350 may be either a power plane or a ground plane.

As shown in FIG. 13, the cut-out area 1303 defines a void that extendsfrom the second surface 122 of the first insulative layer 120 to thefirst surface 111 of the first conductive layer 110 of the first layerstack 1302. Cut-out area 1303 is configured to receive at least aportion of the device 170 therein. In some embodiments, when the secondsurface 122 of the first insulative layer 120 is coupled to the firstsurface 1341 of the second insulative layer 1340, the device 170 may bedisposed in a first-level configuration within the cut-out area 1303,wherein the top surface 171 of the device 170 is disposed below thelevel of the second surface 112 of the first conductive layer 110, suchthat the peripheral edges of the device 170 do not physically contactthe first conductive layer 110. In some embodiments, when the secondsurface 122 of the first insulative layer 120 is coupled to the firstsurface 1341 of the second insulative layer 1340, the top surface 171 ofthe device 170 is disposed below the second surface 112 of the firstinsulative layer 140. In some embodiments, a dielectric material (e.g.,dielectric material 180 shown in FIG. 3) may be used to fill, entirelyor in part, a volume of void space (e.g., void space “V₁” shown in FIG.3) defined by the cut-out area 1303 disposed above, or extendingoutwardly from, the top surface 171 of the device 170.

In some embodiments, as shown in FIG. 13, the cut-out area 1330 definesa void that extends from the second surface 1342 of the secondinsulative layer 1340 to the first surface 1351 of the second conductivelayer 1350 of the second layer stack 1304. Cut-out area 1303 isconfigured to receive at least a portion of the device 1370 therein. Insome embodiments, when the second surface 122 of the first insulativelayer 120 is coupled to the first surface 1341 of the second insulativelayer 1340, the device 1370 may be disposed in a first-levelconfiguration within the cut-out area 1303, wherein the top surface 1371of the device 1370 is disposed below the level of the first surface 1351of the second conductive layer 1350, e.g., the top surface 1371 of thedevice 1370 does not extend beyond the second surface 1342 of the secondinsulative layer 1340.

Cut-out areas 1303 and 1330 may be formed by any suitable process, e.g.,laser cutting, stamping, punching and/or die-cutting, or any combinationof these and other processes, e.g., photo-etching. In some embodiments,the cut-out area 1303 defined in the first layer stack 1302 and/or thecut-out area 1330 defined in the second layer stack 1304 may be formedby fineblanking, or a combination of fineblanking and formingoperations. After fineblanking (or laser cutting, stamping, punching,die-cutting, etc.), one or more cut-out portions 1380 from the firstlayer stack 1302 and/or the second layer stack 1304 (e.g., cut-outportion 1380 associated with the cut-out area 1330) may be retained soas to be available for use as replacement material for filling anyvolume of void space defined by one or more cut-out areas, e.g., cut-outarea 1303 and/or the cut-out area 133, and/or for minimizingdiscontinuity in a ground plane (or power plane).

In some cases, one or more cut-out areas defined through the first layerstack 1302 and/or the second layer stack 1304 may not be utilized duringPCB assembly (or, later, a component may be removed from the PCB 1300).In cases such as those, the retained cut-out portions 1380 may be usedas replacement material, e.g., to close the opening in the ground plane(or power plane) defined by the cut-out area, thereby minimizingdiscontinuity in the ground plane (or power plane), e.g., to avoiddegrading electrical performance.

In some embodiments, one or more gap areas (e.g., first gap area 632and/or second gap area 634 shown in FIG. 6, or gap area 736 shown inFIG. 7) disposed in adjoining relation to the cut-out area 1303 may beprovided to the first layer stack 1302. In some embodiments, when thesecond surface 122 of the first insulative layer 120 of the first layerstack 1302 is coupled to the first surface 1341 of the second insulativelayer 1340 of the second layer stack 1304, the device 170 may bedisposed in a second-level configuration, wherein a first portion of thedevice 170 is disposed within the cut-out area 1303 and a second portionincluding the top surface 171 of the device 170 is disposed (e.g., inrelation to the first conductive layer 110) outwardly of the firstsurface 111 and/or the second surface 112 of the first conductive layer110.

One or more gap areas (e.g., first gap area 632 and/or second gap area634 shown in FIG. 6, or gap area 736 shown in FIG. 7) disposed inadjoining relation to the cut-out area 1330 may additionally, oralternatively, be provided to the second layer stack 1304. In someembodiments, when the second surface 122 of the first insulative layer120 of the first layer stack 1302 is coupled to the first surface 1341of the second insulative layer 1340 of the second layer stack 1304, thedevice 1370 may be disposed in a second-level configuration, wherein afirst portion of the device 1370 is disposed within the cut-out area1330 and a second portion including the top surface 1371 of the device1370 is disposed (e.g., in relation to the second conductive layer 1350)outwardly of the first surface 1351 and/or the second surface 1352 ofthe second conductive layer 1350.

FIG. 14 shows a portion of a PCB 1400 with layer stacks separatedaccording to an embodiment of the present disclosure. PCB 1400 includesthe first layer stack 1302 shown FIG. 13 including the first cut-outarea 1303 defined therethrough and the circuit 1376. PCB 1400 includes asecond layer stack 1404 including a second cut-out area 1430 definedtherethrough. Although only two cut-out areas 1303 and 1430 are shown inFIG. 14 for ease of illustration, it is to be understood that PCB 1400may include any number of cut-areas defined in the first layer stack1302 and/or the second layer stack 1404.

Second layer stack 1404 includes a second insulative layer 1440. Secondinsulative layer 1440 generally includes a first surface 1441 and anopposite second surface 1442. Second insulative layer 1440 may include asingle layer, or a plurality of layers, of any suitable dielectric orinsulating material disposed between the first and second surfaces 1441and 1442, respectively. In some embodiments, the second layer stack 1404includes a second conductive layer 1450 including a first surface 1451and an opposite second surface 1452. In some embodiments, as shown inFIG. 14, second surface 1452 of the second conductive layer 1450 isdisposed on the second surface 1442 of the second insulative layer 1440.In an alternative embodiment not shown, one or more layers of anysuitable material may be disposed between the second surface 1442 of thesecond insulative layer 1440 and the second surface 1452 of the secondconductive layer 1450, e.g., to form a bond therebetween. In someembodiments, the second conductive layer 1450 may be either a powerplane or a ground plane.

Second layer stack 1404 includes a prepreg layer 1445 disposed inassociation with the second insulative layer 1440. Prepreg layer 1445generally includes a first surface 1447 and an opposite second surface1446. In some embodiments, as shown in FIG. 14, second surface 1446 ofthe prepreg layer 1445 is disposed on the first surface 1441 of thesecond insulative layer 1440. Circuit 176 may be disposed in associationwith the first surface 1447 of the prepreg layer 1445. second conductivelayer 1350 of FIG. 13 disposed on a first surface 1441 of a secondinsulative layer 1440, a prepreg layer 1445 disposed on an oppositesecond surface 1442 of the second insulative layer 1440, and a cut-outarea 1430 defined therethrough.

As shown in FIGS. 13 and 14, the first layer stack 1302 includes acircuit 1376 disposed in association with a first insulative layer 120.Circuit 1376 generally includes a device 1370 and one or morestrip-lines 1360 disposed on a second surface 122 of the firstinsulative layer 120. Cut-out area 1430 defined in the second layerstack 1404 is configured to receive at least a portion of the device1370 therein.

In some embodiments, the second conductive layer 1350 may be either apower plane or a ground plane. Second insulative layer 1440 may includea single layer, or a plurality of layers, of any suitable dielectric orinsulating material disposed between the first and second surfaces 1441and 1442, respectively. Second insulative layer 1440 is similar to thesecond insulative layer 1340 of FIG. 13 and further description thereofis omitted in the interests of brevity.

Prepreg layer 1445 generally includes a first surface 1447 and anopposite second surface 1446. In some embodiments, as shown in FIG. 14,the second surface 1446 of the prepreg layer 1445 is disposed on thefirst surface 1441 of the second insulative layer 1440 of the secondlayer stack 1404. Prepreg layer 1445 is similar to the prepreg layer1225 shown in FIG. 12 and further description thereof is omitted in theinterests of brevity. In an alternative embodiment not shown, the firstlayer stack 1302 may additionally, or alternatively, include a prepreglayer, e.g., a prepreg layer (not shown) may be disposed on the secondsurface 122 of the first insulative layer 120 of the first layer stack1302.

PCB 1400 may employ the dielectric material 180 and/or one or moresheets of electrically-conductive material 190 of the PCB embodimentshown in FIG. 3. In some embodiments, dielectric material 180 (FIG. 3)may be used to at least partially fill the void defined by the cut-outarea 1303. In some embodiments, dielectric material 180 mayadditionally, or alternatively, be used to at least partially fill thevoid defined by the cut-out area 1430 shown in FIG. 14.

In some embodiments, a first sheet of electrically-conductive material190 (FIG. 3) may additionally, or alternatively, be disposed over thecut-out area 1303 of the first layer stack 1302 shown in FIG. 14.Additionally, or alternatively, a second sheet ofelectrically-conductive material 190 may be disposed over the cut-outarea 1430 of the second layer stack 1404 shown in FIG. 14.

It is to be understood that the configuration of layers between thecircuit 1376 and the first conductive layer 110 of the first layer stack1302, and the configuration of layers between the circuit 176 and thesecond conductive layer 1350 of the second layer stack 1404, are merelyillustrative and non-limiting examples of layer stack-ups, and that PCBlayer stacks including a conductive layer (e.g., ground or power plane)and one or more cut-out areas (e.g., two cut-out areas 1303 and 1430shown in FIG. 14) defined therethrough according to embodiments of thepresent disclosure may utilize many different configurations of layerstack-ups, some with fewer, or additional, layers than depicted in thefirst and second layer stacks of FIG. 14.

FIGS. 15 and 16A show a portion of a PCB 1500 according to an embodimentof the present disclosure. PCB 1500 includes a first layer stack 1603.First layer stack 1603 includes a first insulative layer 1620 and afirst conductive layer 1610. First layer stack 1603 may include one ormore cut-out areas (e.g., cut-out area 1530) defined therethrough. Insome embodiments, the first conductive layer 1610 may be a power planeor a ground plane. First insulative layer 1620 and the first conductivelayer 1610 are similar to the first insulative layer 120 and the firstconductive layer 110, respectively, of the first stack layer 102 shownin FIG. 3 and further description thereof is omitted in the interests ofbrevity.

PCB 1500 includes a second layer stack 1604. Second layer stack 1604includes a second insulative layer 1640 and a second conductive layer1650. In some embodiments, the second conductive layer 1650 may be apower plane or a ground plane. Second insulative layer 1640 and thesecond conductive layer 1650 are similar to the second insulative layer140 and the second conductive layer 150, respectively, of the secondstack layer 104 shown in FIG. 3 and further description thereof isomitted in the interests of brevity. In an alternative embodiment notshown, the second layer stack 1604 includes one or more cut-out areasdefined therethrough.

In some embodiments, as shown in FIG. 16A, first layer stack 1603includes a third insulative layer 1660 disposed in association with thefirst conductive layer 1610. Third insulative layer 1660 may include asingle layer, or a plurality of layers, of any suitable dielectric orinsulating material. A prepreg layer and/or other suitable material (notshown) may be disposed between the third insulative layer 1660 and thefirst conductive layer 1610, e.g., to form a bond therebetween. In analternative embodiment not shown, the third insulative layer 1660 may bedisposed in association with the second conductive layer 1650.

PCB 1500 includes a first signal layer 115. In some embodiments, asshown in FIG. 16A, first signal layer 115 is disposed between the firstand second conductive layers 1610 and 1650, respectively. First signallayer 115 may include any suitable configuration of conductive traces,e.g., three conductive traces 160, 54 and 51 shown in FIGS. 15 and 16A.In some embodiments, one or more conductive traces, e.g., traces 160, 54and/or 51, may be formed of one or more strip-line traces disposed onthe first signal layer 115.

In some embodiments, as shown in FIG. 16A, first signal layer 115 isdisposed between the first and second insulative layers 1620 and 1640,respectively, which, in turn, are disposed between the first and secondconductive layers 1610 and 1650, respectively. First insulative layer1620 and/or the second insulative layer 1640 may include a single layer,or a plurality of layers, of any suitable dielectric or insulatingmaterial. In some embodiments, a prepreg layer (e.g., prepreg layer 1445shown in FIG. 14), and/or other suitable material, may be disposedbetween the first and second insulative layers 1620 and 1640,respectively, e.g., to form a bond therebetween.

In some embodiments, as shown in FIG. 16A, the third insulative layer1660 includes the cut-out area 1530, and may include one or more gapareas (e.g., gap area 1536 shown in FIGS. 15 and 16A) disposed inadjoining relation to the cut-out area 1530. In some embodiments, one ormore surfaces of the first insulative layer 1620, the first conductivelayer 1610, and/or the third insulative layer 1660 disposed adjacent tothe outer periphery of the cut-out area 1530 may include one or moregrooves, slots, pockets, channels or other recesses (not shown)configured to accommodate and receive therein one or more portions of adevice, and/or to allow for air circulation around the device, orportion thereof, to increase heat dissipation.

PCB 1500 includes a second signal layer 215 disposed on, or otherwiseassociated with, the third insulative layer 1660. Second signal layer215 may include any suitable configuration of conductive traces, e.g.,six conductive traces 60, 61, 62, 63, 64 and 65 shown in FIG. 15. Insome embodiments, the conductive traces 60, 61, 62 63, 64 and/or 65 maybe formed of one or more microstrip traces disposed on the second signallayer 215. One or more electrical devices, electrical and/or electroniccomponents, and/or connectors may be disposed in association with thesecond signal layer 215 and/or electrically-coupled to one or moreconductive traces disposed on the second signal layer 215. PCB 1500 mayinclude one or more via holes, e.g., three via holes 70, 71 and 72,configured to electrically couple one or more elements of the secondsignal layer 215 to one or more elements of the first signal layer 115.

In some embodiments, as shown in FIG. 15, PCB 1500 includes two devices1580 and 1581 disposed in association with the second signal layer 215.Devices 1580 and 1581 may be electrically-coupled to one another by oneor more conductive traces, e.g., two conductive traces 62 and 63disposed on the second signal layer 215. Additionally, or alternatively,devices 1580 and 1581 may be electrically-coupled to one another by apath including three conductive traces, wherein two conductive traces 64and 65 are disposed in association with the second signal layer 215 andconnected by two via holes 71 and 72, respectively, to a conductivetrace 54 disposed in association with the first signal layer 115.

PCB 1500 includes the circuit 176 and the device 170 of the PCBembodiments shown in FIG. 3 and FIGS. 12 through 14. In the embodimentshown in FIGS. 15 and 16A, the circuit 176 is disposed in associationwith the first signal layer 115 and electrically-coupled to one or moreconductive traces 160 disposed on the first signal layer 115. Device1580 may be electrically-coupled to the device 170 by a conductive trace60 disposed on the first signal layer 115 connected by a via hole 70 tothe one or more conductive traces 160.

As shown in FIG. 16A, the first layer stack 1603 includes the firstconductive layer 1610 disposed between the third insulative layer 1660and the first insulative layer 1620, and a cut-out area 1530 defining avoid therethrough. PCB 1500 may include a gap area 1536 disposed aroundthe outer periphery of the cut-out area 1530, e.g., in adjoiningrelation to the cut-out area 1530. As best shown in FIG. 15, device 170is disposed within the cut-out area 1530. Cut-out area 1530 generallyextends from the first signal layer 115 to an opening 200 defined in thesecond signal layer 215. In an alternative embodiment not shown, PCB1500 may include a plurality of gap areas (e.g., first gap area 632 andsecond gap area 634 shown in FIG. 6), e.g., disposed in adjoiningrelation to the cut-out area 1530.

FIG. 16B shows a portion of a PCB 1600 according to an embodiment of thepresent disclosure. PCB 1600 includes the second layer stack 1604 of thePCB 1500 including the second insulative layer 1640 and the secondconductive layer 1650 shown in FIG. 16A. PCB 1600 is similar to the PCB1500 shown in FIG. 16A, except that, instead of the first layer stack1603 of the PCB 1500 shown in FIG. 16A, the PCB 1600 includes a firstlayer stack 1602 and a third layer stack 1606. First layer stack 1602 ofthe PCB 1600 includes the first insulative layer 1620 and the firstconductive layer 1610 shown in FIG. 16A. First layer stack 1602 furtherincludes a portion of the cut-out area 1530 defining a void that extendsfrom the first signal layer 115 through the first conductive layer 1610.Third layer stack 1606 of the PCB 1600 includes the third insulativelayer 1660 shown in FIG. 16A disposed in association with the secondconductive layer 1650 of the first layer stack 1602. A prepreg layerand/or other suitable material (not shown) may be disposed between thethird insulative layer 1660 and the first conductive layer 1610. Asshown in FIG. 16B, third layer stack 1606 includes a portion of thecut-out area 1530 defined therethrough.

It is to be understood that the configuration of the first layer stack1603 of the PCB 1500, and the configuration of the first layer stack1602 of the PCB 1600, are merely illustrative and non-limiting examplesof layer stack-ups, and that PCB layer stacks including a conductivelayer (e.g., ground or power plane) and one or more cut-out areas (e.g.,two cut-out areas 1303 and 1430 shown in FIG. 14) defining a voidextending therethrough according to embodiments of the presentdisclosure may utilize many different configurations of layer stack-ups,some with fewer, or additional, layer stacks than depicted in the PCBembodiments of FIGS. 15, 16A and 16B.

FIG. 17 shows a portion of a PCB 1700 according to an embodiment of thepresent disclosure. PCB 1700 includes a first signal layer 315. PCB 1700generally includes the first conductive layer 1610, the secondconductive layer 1650, and the second signal layer 215 of the PCB 1500shown in FIGS. 15 and 16A.

First signal layer 315 includes one or more electrically-conductivetraces disposed in association with the insulative layer 1740. One ormore electrical devices, electrical and/or electronic components, and/orconnectors may be disposed in association with the first signal layer315 and/or electrically-coupled to one or more conductive tracesdisposed on the first signal layer 315. First signal layer 315 mayinclude any suitable configuration of conductive traces, e.g., fourconductive traces 1761, 1762, 1763 and 1764 shown in FIG. 17. In someembodiments, the conductive traces 1761, 1762, 1763 and/or 1764 may beformed of one or more microstrip traces disposed on the first signallayer 315. Second signal layer 215 may include any suitableconfiguration of conductive traces, e.g., six conductive traces 60, 61,62, 63, 64 and 65 shown in FIG. 15. PCB 1700 may include one or moredevices (e.g., device 1581) disposed in operative association with thesecond signal layer 215 and/or the first signal layer 315.

PCB 1700 includes an inner or first layer stack 1720 disposed betweenthe first and second conductive layers 1610 and 1650, respectively.First layer stack 1720 may include one or more layers of any suitabledielectric or insulating material. First layer stack 1720 may includeone or more layers of prepreg material (not shown). In an alternativeembodiment not shown, first layer stack 1720 may include the firstconductive layer 1610 and/or the second conductive layer 1650.

One or more signal layers may be disposed in association with the firstlayer stack 1720. As shown in FIG. 17, PCB 1700 includes an asymmetricstrip-line configuration including two internal signal layers 1716 and1717 disposed within the inner layer stack 1720. Asymmetric strip-lineimpedance calculations may depend on a variety of factors, such asmaterial properties of the material(s) forming the insulative layers,the configuration of insulative layers, and the configuration of signallayers, among other factors.

PCB 1700 includes a second layer stack 1707 including an insulativelayer 1660 disposed in association with the first conductive layer 1610.Insulative layer 1660 may include a single layer, or a plurality oflayers, of any suitable dielectric or insulating material. A prepreglayer and/or other suitable material (not shown) may be disposed betweenthe insulative layer 1660 and the first conductive layer 1610, e.g., toform a bond therebetween. In an alternative embodiment not shown,wherein the first layer stack 1720 includes the first conductive layer1610, the second layer stack 1707 includes the insulative layer 1660,and may include prepreg and/or other suitable material, e.g., to form abond between the insulative layer 1660 and the first conductive layer1610.

As shown in FIG. 17, second signal layer 215 is disposed in associationwith the second layer stack 1707. One or more metal-filledthrough-holes, or vias (not shown), may be disposed in association withthe insulative layer 1660, and may be configured to electrically-coupleone or more elements of the second signal layer 215 to one or moreelements of the internal signal layer 1716 and/or the internal signallayer 1717.

In some embodiments, as shown in FIG. 17, PCB 1700 includes a thirdlayer stack 1709 including an insulative layer 1740 disposed inassociation with the second conductive layer 1650. In an alternativeembodiment not shown, wherein the first layer stack 1720 includes thesecond conductive layer 1650, the third layer stack 1709 includes theinsulative layer 1740, and may include prepreg and/or other suitablematerial, e.g., to form a bond between the insulative layer 1740 and thesecond conductive layer 1650.

First signal layer 315 is disposed in association with the second layerstack 1709. One or more microstrip traces, e.g., four traces 1761, 1762,1763 and 1764, may be disposed on the insulative layer 1740, and mayroute signal, power, and/or ground lines to and from the circuitrydisposed in association with the insulative layer 1740. One or moremetal-filled through-holes, or vias (not shown), may be disposed inassociation with the insulative layer 1740, and may be configured toelectrically-couple one or more elements of the first signal layer 315to one or more elements of the internal signal layer 1716 and/or theinternal signal layer 1717.

Hereinafter, methods of manufacturing a PCB in accordance with thepresent disclosure are described with reference to FIGS. 18 through 26.It is to be understood that the steps of the methods provided herein maybe performed in combination and in a different order than presentedherein without departing from the scope of the disclosure. In themethods of manufacturing printed circuit boards provided herein, the“first” layer stack 102 shown in FIG. 3 may be referred to as “second”layer stack 102 and the “second” layer stack 104 of FIG. 3 may bereferred to as “first” layer stack 104, for ease of explanation.

FIG. 18 is a flowchart illustrating a method (shown generally as 1800 inFIG. 18) of manufacturing a PCB in accordance with an embodiment of thepresent disclosure. In step 1810, a first layer stack 104 is provided.First layer stack 104 includes a first electrically-insulating layer140. First electrically-insulating layer 140 includes a first surface141 and one or more electrically-conductive traces 160 disposed on thefirst surface 141.

In step 1820, a second layer stack 102 is provided. Second layer stack102 includes a second electrically-insulating layer 120 and a firstelectrically-conductive layer 110. The second electrically-insulatinglayer 120 includes a first surface 121 and an opposite second surface122. First electrically-conductive layer 110 may be disposed on thefirst surface 121 of the second electrically-insulating layer 120.Alternatively, a prepreg layer and/or other suitable material (notshown) may be disposed between the first surface 121 of secondelectrically-insulating layer 120 and the first electrically-conductivelayer 110, e.g., to form a bond therebetween.

Second layer stack 102 includes a cut-out area 130 defining a void thatextends therethrough. Cut-out area 130 is configured to receive thereinat least a portion of a device 170 to be coupled to the first surface141 of the first electrically-insulating layer 140 and/orelectrically-coupled to one or more of the one or moreelectrically-conductive traces 160.

In step 1830, the first surface 141 of the first electrically-insulatinglayer 140 is coupled to the second surface 122 of the secondelectrically-insulating layer 120. The step 1830 may include the step oforienting the first layer stack 104 and the second layer stack 102 inrelation to one another such that the first surface 141 of the firstelectrically-insulating layer 140 opposes the second surface 122 of thesecond electrically-insulating layer 120. The step 1830 may furtherinclude positioning the first layer stack 104 and the second layer stack102 in relation to one another such that the cut-out area 130 ispositioned to receive at least a portion of the device 170 therein whenthe first surface 141 of the first electrically-insulating layer 140 isplaced in contact with the second surface 122 of the secondelectrically-insulating layer 120.

The above-described method 1800 of manufacturing a PCB may additionallyinclude the step of mounting the device 170 on the first layer stack104. The mounting step may include the step of electrically-coupling thedevice 170 to one or more of the one or more electrically-conductivetraces 160.

In some embodiments, the above-described method 1800 of manufacturing aPCB may additionally, or alternatively, include one or more of the stepsshown in FIG. 21, FIG. 22 and/or FIG. 23, which are described later inthis description.

The above-described method 1800 of manufacturing a PCB may additionallyinclude the step of coupling a third layer stack (e.g., third layerstack 1606 shown in FIG. 16B, or third layer stack 1709 shown in FIG.17) to the first layer stack 104 (or the second layer stack 102). Thethird layer stack may include a third electrically-insulating layer(e.g., 1660 shown in FIG. 16B) and a signal layer 215 disposed inassociation with a first surface of the third electrically-insulatinglayer.

FIG. 19 is a flowchart illustrating a method (shown generally as 1900 inFIG. 19) of manufacturing a PCB in accordance with an embodiment of thepresent disclosure. In step 1910, a first layer stack 102 is provided.First layer stack 102 includes a first electrically-conductive layer 110and a first electrically-insulating layer 120. Firstelectrically-insulating layer 120 includes a first surface 121 and anopposite second surface 122. First electrically-conductive layer 110 isdisposed on the first surface 121 of the first electrically-insulatinglayer 120.

In step 1920, a second layer stack 104 is provided. The second layerstack 104 includes a second electrically-insulating layer 140. Secondelectrically-insulating layer 140 includes one or moreelectrically-conductive traces 160 disposed on a first surface 141thereof.

In step 1930, a device 170 is mounted on the first surface 141 of thesecond electrically-insulating layer 140 such that the device 170 iselectrically-coupled to at least one of the one or moreelectrically-conductive traces 160.

In step 1940, the first layer stack 102 is provided with a cut-out area130 defining a void that extends from the second surface 122 of thefirst electrically-insulating layer 120 to the first surface 111 of thefirst electrically-conductive layer 110. Cut-out area 130 is configuredto receive at least a portion of the device 170 therein.

In step 1950, the first surface 141 of the secondelectrically-insulating layer 140 is brought in contact with the secondsurface 122 of the first electrically-insulating layer 120 such that atleast a portion of the device 170 is disposed within at least a portionof the cut-out area 130.

In some embodiments, the above-described method (shown generally as 1900in FIG. 19) may include one or more of the additional steps shown inFIG. 21.

FIG. 20 is a flowchart illustrating a method of manufacturing a PCB inaccordance with an embodiment of the present disclosure. In step 2010, afirst electrically-insulating layer 120 is provided. Firstelectrically-insulating layer 120 includes a first surface 121 and anopposite second surface 122.

In step 2020, a first electrically-conductive layer 110 is provided onthe first surface 121 of the first electrically-insulating layer 120.

In step 2030, a cut-out area 130 is provided that defines a void thatextends from the second surface 122 of the first electrically-insulatinglayer 120 to the first surface 111 of the first electrically-conductivelayer 110.

In step 2040, a second electrically-insulating layer 140 is providedthat includes a first surface 141 and an opposite second surface 142.

In step 2050, a second electrically-conductive layer 150 is provided onthe second surface 142 of the second electrically-insulating layer 140.

In step 2060, one or more electrically-conductive traces 160 areprovided on the first surface 141 of the second electrically-insulatinglayer 140.

In step 2070, a device 170 is mounted on the first surface 141 of thesecond electrically-insulating layer 140 such that the device 170 iselectrically-coupled to at least one of the one or moreelectrically-conductive traces 160.

In step 2080, the second surface 122 of the firstelectrically-insulating layer 120 is placed in contact with the firstsurface 141 of the second electrically-insulating layer 140 such that atleast a portion of the device 170 is disposed within at least a portionof the cut-out area 130.

In some embodiments, the above-described method (shown generally as 2000in FIG. 20) may include one or more of the additional steps shown inFIGS. 21, 22 and/or 23.

FIG. 21 is a flowchart illustrating steps of a method for manufacturinga PCB in accordance with an embodiment of the present disclosure. Instep 2110, a determination is made whether there remains any portion(e.g., volume) of the void defined by the cut-out area 130 extendingoutwardly from (e.g., above) the device 170.

In step 2120, if it is determined that there remains a volume of thevoid defined by the cut-out area 130 above the device 170, then adetermination is made whether the volume of the void defined by thecut-out area 130 above the device 170 is to be at least partially filledwith a dielectric material 180 other than a vacuum or a gas (or mixtureof gases, such as air).

In step 2130, if it is determined that the volume of the void defined bythe cut-out area 130 above the device 170 is to be at least partiallyfilled with a dielectric material 180 other than a vacuum or a gas or agas mixture, then at least partially filling the volume of the void withthe dielectric material other than a vacuum or a gas or a mixture ofgases.

In some embodiments, the above-described method (shown generally as 2100in FIG. 21) may include one or more of the additional steps shown inFIG. 22 and/or FIG. 23.

FIG. 22 is a flowchart illustrating steps of a method for manufacturinga PCB in accordance with an embodiment of the present disclosure. Instep 2210, a sheet of electrically-conductive material is provided. Thesheet of electrically-conductive material 190 includes a first portion194 configured to cover the cut-out area 130 when a second portion 195of the sheet of electrically-conductive material 190 is disposed on thefirst surface 111 of the first electrically-conductive layer 110. Insome embodiments, the sheet of electrically-conductive material 190 maybe a conductive tape, e.g., carbon conductive tape, copper conductivetape, silver conductive adhesive sheet.

In step 2220, the second portion 195 of the sheet of theelectrically-conductive material 190 is coupled to at least a portion ofthe first surface 111 of the first electrically-conductive layer 110. Insome embodiments, prior to the step 2220, an area 113 of the firstelectrically-conductive layer 110, e.g., a portion adjacent to the outerperipheral edges of the cut-out area 130, may be removed, e.g.,photo-etched. In some embodiments, the first electrically-conductivelayer 110 of the first stack 102 may be formed, patterned or otherwisedeposited to eschew the area 113, e.g., to reduce assembly steps and/orfabrication costs, in which case the second portion 195 of the sheet ofelectrically-conductive material 190 may be coupled to the first surface121 of the first electrically-insulating layer 120.

In some embodiments, the above-described method (shown generally as 2200in FIG. 22) may include one or more of the additional steps shown inFIG. 23.

FIG. 23 is a flowchart illustrating steps of a method for manufacturinga PCB in accordance with an embodiment of the present disclosure. Instep 2310, a third electrically-insulating layer 1660 is provided. Thirdelectrically-insulating layer 1660 includes a first surface 1661 and anopposite second surface 1662.

In step 2320, the second surface 1662 of the thirdelectrically-insulating layer 1660 is placed in contact with the firstsurface 111 of the first electrically-conductive layer 110 or the firstsurface 151 of the second electrically-conductive layer 150.

In step 2330, one or more electrically-conductive traces 62, 63 areprovided on the first surface 1661 of the third electrically-insulatinglayer 1660.

FIG. 24 is a flowchart illustrating steps of a method for manufacturinga PCB in accordance with an embodiment of the present disclosure. Instep 2410, a third electrically-insulating layer 1660 is provided. Thirdelectrically-insulating layer 1660 includes a first surface 1661 and anopposite second surface 1662.

In step 2420, the second surface 1662 of the thirdelectrically-insulating layer 1660 is placed in contact with the firstsurface 151 of the second electrically-conductive layer 150.

In step 2430, one or more electrically-conductive traces 62, 63 areprovided on the first surface of the third electrically-insulating layer1660.

FIG. 25 is a flowchart illustrating steps of a method for manufacturinga PCB in accordance with an embodiment of the present disclosure. Instep 2510, a first layer stack 702 and a second layer stack 104 areprovided. The first layer stack 1603 includes a firstelectrically-conductive layer 1610 and first and thirdelectrically-insulating layers 1620 and 1660, respectively, disposed onopposite sides of the first electrically-conductive layer 1610. Thesecond layer stack 1604 includes a second electrically-insulating layer1640 having a first surface 1641 and an opposite second surface 1642 anda second electrically-conductive layer 1640 disposed on the secondsurface 1642 of the second electrically-insulating layer 1650.

In step 2520, a device 170 or 1070 is provided on the first surface 1641of the second electrically-insulating layer 1640 such that the device170 or 1070 is electrically-coupled to one or more of the one or moreelectrically-conductive traces 160 disposed on the first surface 1641 ofthe second electrically-insulating layer 1640.

In step 2530, the first layer stack 1603 is provided with a cut-out area1530 defining a void that extends from an outer surface of the firstelectrically-insulating layer 1620 to an outer surface 1661 of thirdelectrically-insulating layer 1660. The cut-out area 1530 is configuredto receive at least a portion of the device 170 or 1070 therein.

In step 2540, the first surface 1641 of the secondelectrically-insulating layer 1640 is placed in contact with the outersurface of the first electrically-insulating layer 1620 such that atleast a portion of the device 170 or 1070 is disposed within at least aportion of the cut-out area 1530.

FIG. 26 is a flowchart illustrating steps of a method for manufacturinga PCB in accordance with an embodiment of the present disclosure. Instep 2610, a pattern of one or more electrically-conductive traces 62,63 is provided on one or more areas of the outer surface 1661 of thethird electrically-insulating layer 1660. The one or more areas arespaced apart from the cut-out area 1530.

In step 2620, one or more devices 1581 are provided on the outer surface1661 of the third electrically-insulating layer 1660 such that one ormore of the one or more devices 1581 is electrically-coupled to one ormore of the one or more electrically-conductive traces 62, 63 disposedon the outer surface 1661 of the third electrically-insulating layer1660.

Various embodiments of the above-disclosed PCBs include at least onelayer stack that includes an electrically-conductive layer (e.g., aground plane or a power plane), an electrically-insulating layer, andone or more cut-out areas defining a void that extends therethrough.

Providing PCBs including one or more layer stacks that include one ormore cut-out areas configured to receive at least a portion of a devicetherein according to embodiments of the present disclosure may allow formodularity in the design of PCBs and/or may allow for ease of assembly,e.g., allowing for electrical connection of the device(s) to one or moresignal layers.

Various embodiments of the presently-disclosed PCBs including one ormore cut-out areas defined in one or more layer stacks may be suitablefor use in a variety of PCB applications across a wide range ofindustries, e.g., the medical, military, aerospace, telecommunication,and automotive industries, in a broad spectrum of technologies.

Although embodiments have been described in detail with reference to theaccompanying drawings for the purpose of illustration and description,it is to be understood that the inventive processes and apparatus arenot to be construed as limited thereby. It will be apparent to those ofordinary skill in the art that various modifications to the foregoingembodiments may be made without departing from the scope of thedisclosure.

What is claimed is:
 1. A printed circuit board (PCB), comprising: afirst layer stack including a first electrically-insulating layer, afirst electrically-conductive layer, and a cut-out area defining a voidthat extends through the first layer stack, the firstelectrically-insulating layer including a first surface and an oppositesecond surface, the first electrically-conductive layer disposed on thefirst surface of the first electrically-insulating layer; a second layerstack coupled to the first layer stack, the second layer stack includinga second electrically-insulating layer, the secondelectrically-insulating layer including a first surface and an oppositesecond surface; an electrically-conductive trace disposed on the firstsurface of the second electrically-insulating layer; a device at leastpartially disposed within the cut-out area and electrically-coupled tothe electrically-conductive trace; and a sheet ofelectrically-conductive material including a first portion covering thecut-out area and a second portion disposed on a portion of the firstsurface of the first electrically-insulating layer.
 2. The PCB of claim1, wherein the second layer stack further includes a secondelectrically-conductive layer disposed on the second surface of thesecond electrically-insulating layer.
 3. The PCB of claim 1, wherein thecut-out area is configured to receive therein at least a portion of thedevice.
 4. The PCB of claim 3, wherein a height of the device is lessthan a thickness of the first electrically-insulating layer.
 5. The PCBof claim 3, wherein the device includes a top surface and a bottomsurface.
 6. The PCB of claim 5, wherein the firstelectrically-conductive layer includes a first surface and an oppositesecond surface, and the top surface of the device is disposed below thesecond surface of the first electrically-conductive layer.
 7. The PCB ofclaim 6, wherein the void defined by the cut-out area includes a firstvolume of void space defined between the top surface of the device and aplane containing the first surface of the first electrically-conductivelayer.
 8. The PCB of claim 7, further comprising dielectric materialdisposed in at least a portion of the first volume of void space.
 9. ThePCB of claim 8, further comprising a sheet of electrically-conductivematerial including a first portion configured to cover the cut-out area.10. The PCB of claim 9, further comprising a third layer stack coupledto the first layer stack, the third layer stack including a thirdelectrically-insulating layer having a first surface.
 11. The PCB ofclaim 10, further comprising a signal layer disposed in association withthe first surface of the third electrically-insulating layer.
 12. ThePCB of claim 11, further comprising a cut-out area defining a void thatextends from the first surface of the third electrically-insulatinglayer to the first surface of the second electrically-insulating layer.13. The PCB of claim 3, wherein a height of the device is greater than aheight of the first layer stack.
 14. The PCB of claim 13, furthercomprising one or more gap areas disposed in adjoining relation to thecut-out area.
 15. The PCB of claim 14, wherein the one or more gap areasare configured to at least one of physically isolate the device from thefirst electrically-conductive layer or electrically isolate the devicefrom the first electrically-conductive layer.
 16. The PCB of claim 15,further comprising a heat sink layer disposed in association with thetop surface of the device.
 17. The PCB of claim 1, wherein the secondsurface of the first electrically-insulating layer is coupled to thefirst surface of the second electrically-insulating layer.
 18. The PCBof claim 1, wherein the first electrically-conductive layer is a groundplane.
 19. The PCB of claim 1, wherein the first electrically-conductivelayer is a power plane.